Exponential growth is when a numerical value increases by a fixed proportion in each unit of time (or some other variable). For example, if the value of gold grows by 10% each year. When this happens the value at time t is Kt where K is a constant greater than 1, or alternatively eλt where λ = ln(K), the natural logarithm of K. Exponential growth increases faster than any positive power of t.
Used on pages 68, 334